The purpose of the proposed research is to correlate the effects of aging and of various disease states on the functional capability and biosynthetic pathways of testicular steroid production. Alterations in the types of steroids produced with aging or with various diseases other than aging may be responsible for the physical, mental and biochemical changes occurring with advancing years. The study will include the evaluation of diurnal rhythms and ability of the testis to respond to gonadotropin. Information gained from these studies will be helpful in understanding the aging process and the role of reproductive function in various diseases of aging.